The present invention relates to a process for the froth flotation of complex metal compounds. What is in question is in particular an ore-dressing process by means of a collector and a frother in which electrochemical control of the flotation conditions creates optimum conditions for the flotation.
In general, froth flotation is carried out using a collector which should be specific as regards the mineral being frothed in order that the result of the froth flotation be optimal. By means of the collector the mineral is caused to adhere to air bubbles and to rise to the surface of the material being treated by froth flotation. It has been presented that adherence to the surface of the desired mineral is affected by the relative wettability of the surfaces of the various minerals. The free energy of the surface is often intentionally reduced by adding, for example, heteropolar surface-active agents.
Collectors which collect only a certain mineral from among several other minerals are very difficult to find, especially when high demands of effectiveness are also set on the collector. The composition of the mineral varies continually and, on the other hand, the surface properties of many different minerals greatly resemble each other. The mineral formation environments, etc., for their part affect the properties of minerals, and so the behavior of the collector is not easy to predict. Usually it is necessary to settle for compromises as regards specificity and effectiveness, and the separation conditions must be created by means of regulating reagents and pH changes.
Endeavours have been made to improve in several ways the predictability of the behavior of collectors. New collectors have been developed, and attempts have been made to improve the effectiveness of the collector agent by oxidizing the agent electrochemically during the treatment of the ore slurry, and on the other hand, attempts have been made to affect the properties of the ore by reducing the oxidized ore by means of an electric current during the pre-treatment of the ore.
Furthermore, U.S. Pat. No. 3,883,421 to cutting et al discloses a method for the froth flotation of ore and for the recovery of the valuable products present in it by maintaining the redox potential measured from the flotation cell at a certain predetermined value. The value is influenced by adjusting the quantity of the chemicals such as sulfide and xanthate fed into the cell, as the potential measured tends to change from the predetermined value.
However, no advantage is gained by the method in question in the case of complex ore, since if a certain redox potential is selected in advance and the collector, and perhaps also other chemicals, is added, the collector adheres to the surface of one as well as another mineral, because in the control of the potential it is necessary to pass through a range within which the surface compounds of both minerals to be separated and the collector are stable. A stable compound does not easily leave the surface and, in addition, it is easily stabilized by the frother and the oxidized form of the collector. In the method in question of said patent direct measuring of the concentration of collector in the slurry is not used, and for this reason oxidized, poorly soluble forms of the collector are always formed during the control of the potential in question. Since the redox potential is measured in the method, which means unselective measurement by means of, for example, a Pt electrode, and since the collector concentration control is carried out by observing the quality of the concentrate, the variation in the concentration of collector is very high, which for its part results in an ample presence of oxidized forms of the collector, such as dixanthagen, and a poor flotation outcome.
The object of the present invention is to provide a process by means of which the separation is really optimized and by means of which different valuable constituents can be separated, each separately, or by means of which it is possible in most cases to recover all minerals from the ore by joint froth flotation, if so desired. Furthermore, by means of the process according to the invention it is simple to prevent the formation of compounds which have a disadvantageous effect on the separation process. This is all achieved by the process the main characteristics of this invention which are given in the accompanying claims.